The invention relates to a radial compressor, particularly for an exhaust gas turbocharger of an internal combustion engine and also to a motor vehicle with an internal combustion engine and a turbocharger having a radial compressor arranged in an intake section of the internal combustion engine.
The development of charged internal combustion engines for utility or passenger motor vehicles with a desired torque behavior require increasingly broadened compressor characteristic fields. The compressor characteristic field, in which the relation of the starting pressure to the input pressure of the compressor is plotted with regard to the mass flow rate, is limited on the one side by the so-called surge line of the compressor, that is, the minimum possible volume flow, and on the other side by the so-called choke line of the compressor, that is, the maximum possible volume flow. In the region between the surge and the choke line, a stable operation of the compressor and thus of the associated internal combustion engine is possible. With a given nominal point and a corresponding nominal flow rate, the surge line position is also determined by radial compressors in a decisive manner. The torque line with maximum torques of the associated internal combustion engines is thus determined up to the average engine speeds by the surge line of the radial compressor. On the left of the surge line, with smaller mass flow rates, a stable operation of the radial compressor and of the internal combustion engine is no longer ensured due to pump surges. In addition, there is the danger that during an operation below the surge line the radial compressor is damaged already after a relatively short running time. By means of the development of performance graph stabilizing measures (KSM), it is attempted to displace the surge line to low mass flow rates, in order to be able to increase the start-up torque, the acceleration torque and the maximum torque of the associated internal combustion engine.
To this end, radial compressors are known in the state of the art which have a compressor wheel arranged within a compressor housing. The compressor wheel serves for compressing air which is conducted to the compressor wheel via an inflow channel of the compressor housing. The compressed air can subsequently be directed by the compressor wheel into an outflow channel of the compressor housing. The compressor housing additionally comprises a bypass channel as a performance graph measure, which bypass channel has at least a first flow opening upstream of an axial compressor wheel inlet and a second flow opening downstream of the compressor wheel inlet. In an operating region near the surge line, it is hereby possible to discharge the air via the compressor wheel into the bypass channel through the second flow opening and to guide it back to the first compressor wheel inlet after conducting it out of the first flow opening. The mass flow entering the compressor wheel is thereby increased in an advantageous manner. In operating regions near the choke line the flow direction is opposed to the compressor inflow direction. The inflow to the compressor wheel thus takes place on the one hand through the inflow channel and on the other hands via the bypass channel in that air enters the bypass channel through the first flow opening and is supplied to the compressor wheel through the second flow opening. The narrowest cross section of the compressor wheel is hereby partially bypassed in the region of its compressor wheel inlet, so that a higher air mass can be passed through the compressor. It can alternatively be provided that the second flow opening of the bypass channel discharges into the outflow channel downstream of a compressor wheel outflow.
The possiblity that flow swirls and flow displacements form during an operation near the surge line in the region of the rotating compressor wheel is thereby seen to be disadvantageous with the known radial compressors, as this leads to corresponding efficiency losses and instabilities in the compressor operation.
It is thus the object of the present invention to provide a radial compressor of the above-mentioned type which enables a decrease of the surge line and an improved adaptability to the requirements of different types of internal combustion engines in a constructively simple manner.